al. (1998) measured a gradient within the tubes from 80°C inside at the posterior end
to 20°C at the opening, an extreme range for the ends of one animal. Di Meo-Savoie
et al. (2004) placed narrow (3 mm) thermocouples a few centimeters into many
occupied tubes at different East Pacific Rise vents to make extended temperature
recordings. Typical results ran 30° to 80°C and in one case 50° to 110°C for over 4 h
(Fig. 15.5), including one stretch continuously >95°C for 8 min. A controversy over
whether that could possibly be survived by an animal made of lipids and proteins
appears to be settled (although some authors still express uncertainty; apparently it is
almost too much to believe). Structural collagen molecules have been studied in
detail, showing a structure reasonably expected to be especially heat tolerant. Short-
term temperature variations are probably caused by variations in vent flow and in
mixing rates with surrounding water. In addition, Di Meo-Savoie et al. used
microelectrodes and ship-board chemistry to show the unusual chemistry of the water
surrounding pompeii worms: undetectable oxygen (<5 μM), low levels of free sulfide,
but substantial dissolved FeS, seawater concentrations of sulfate (22 to 27 mM), acid
conditions (pH = 5.3 to 6.4), and abundant total dissolved iron (up to >700 μM). All
of those suggest a chemically harsh environment, especially so at >30°C, and no
particular support for sulfide-based chemosynthesis.
Fig. 15.4 Alvinella pompejana, type species of a new family of polychaetes found in
association with hydrothermal vents.
(^) (After Desbruyères & Laubier 1986.)